Understand methionine and methionine targets in the Nutrient Explorer

What it is

Methionine is an essential amino acid.

What it does

Amino acids are the building blocks of proteins. You don’t really need to think about what each amino acid does – your body just needs enough of each amino acid to build the proteins it needs to build. 

Nonessential amino acids are amino acids your body can synthesize from other raw materials. You don’t need to consume nonessential amino acids in your diet, but most normal diets will contain plenty of nonessential amino acids.

Essential amino acids are amino acids your body can’t synthesize from other raw materials. So, you do need to consume essential amino acids in your diet.

Conditionally essential amino acids are amino acids your body can generally synthesize under most circumstances, though there are instances where it may not be able to (due to infancy, advanced age, liver disease, or certain other disease states).

As an essential amino acid, methionine must be consumed from dietary sources.

For more on the general effects of protein, refer to the article on protein.

Recommended intake

The recommended combined intake of methionine and cysteine is 25mg per kilogram of body mass. A normal diet generally has about twice as much methionine as cysteine, so we set the methionine target at 16.5mg/kg.

Likelihood of tracking completeness: Very low

Methionine is not a nutrient food manufacturers are required to disclose on nutrition labels. The vast majority of food manufacturers do not voluntarily list methionine content on nutrition labels, so most branded products in the MacroFactor database lack information on methionine. So, if you’d like to accurately track your methionine intake, you’ll need to make a point of mostly tracking “common foods,” which come from research-grade databases that have full nutrient reporting.

For more on when you can track using branded foods versus common foods when you’re trying to accurately monitor your intake of particular nutrients, you should check out this article.

Likelihood of insufficient intake: Moderate for vegans. Very low for non-vegans.

Insufficient intake of a single essential amino acid can have health consequences. The essential amino acid with the lowest intake relative to physiological needs is referred to as the limiting amino acid. The four most common limiting amino acids are lysine, methionine, threonine, and tryptophan. Lysine or threonine is likely to be the limiting amino acid for individuals who consume most of their total energy from cereal grains (like rice and wheat). Methionine is likely to be the limiting amino acid for individuals who consume most of their total energy from legumes (like beans, chickpeas, and lentils). Tryptophan is likely to be the limiting amino acid for individuals who consume most of their total energy from corn/maize.

Since methionine is a common limiting amino acid, it’s important to consume methionine-rich protein sources (like grains) to negate the risk of a methionine deficiency, if you tend to mostly eat methionine-poor foods (like legumes).

For more on nutrients with a greater likelihood of insufficient or excessive intake, you should check out this article.

Signs of deficiency/insufficiency

The most common signs of a methionine deficiency are the development of non-alcoholic fatty liver disease, weakness, skin lesions, and edema (general swelling and fluid retention). 

Good sources

Omnivores and vegetarians rarely need to worry about consuming adequate methionine, assuming their total protein intake is sufficient. Meat, eggs, and dairy products are generally rich in all of the essential and conditionally essential amino acids.

Among vegan sources of protein, soy-based products, dried seaweed (nori), spirulina, almond-based vegan cheeses, and mycoprotein (like Quorn) are excellent sources of methionine per unit of energy.

Learn more

If you’d like to learn more about micronutrients generally, there’s a five-part series on the MacroFactor website you might enjoy.

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